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| United States Patent |
6,114,094
|
|
Ishiguro
, et al.
|
September 5, 2000
|
Process for making lithographic printing plate
Abstract
There is disclosed a process for making a lithographic printing plate which
comprises subjecting a lithographic printing plate precursor having at
least a hydrophilic layer on a support and a silver thin layer on the
hydrophilic layer to exposure by a laser beam whereby imagewisely removing
the silver thin layer and exposing the hydrophilic layer, wherein the
hydrophilic layer adjacent to the silver thin layer contains at least one
inorganic oxide.
| Inventors:
|
Ishiguro; Hideaki (Tokyo, JP);
Yoshida; Akio (Tokyo, JP);
Takagami; Yuji (Tokyo, JP)
|
| Assignee:
|
Mitsubishi Paper Mills Limited (Tokyo, JP)
|
| Appl. No.:
|
275446 |
| Filed:
|
March 24, 1999 |
Foreign Application Priority Data
| Mar 25, 1998[JP] | 10-077236 |
| Mar 16, 1999[JP] | 11-069786 |
| Current U.S. Class: |
430/302; 430/204; 430/271.1; 430/272.1; 430/328; 430/330; 430/616; 430/964 |
| Intern'l Class: |
G03F 007/20; G03F 007/36; G03F 007/11 |
| Field of Search: |
430/204,616,964,302,328,272.1,271.1,330
|
References Cited
U.S. Patent Documents
| 3971660 | Jul., 1976 | Staehle | 430/204.
|
| 4278756 | Jul., 1981 | Bouldin et al. | 430/616.
|
| 5401611 | Mar., 1995 | Edwards, Sr. et al. | 430/616.
|
| 5916734 | Jun., 1999 | Takagami et al.
| |
| Foreign Patent Documents |
| 10-180976 | Jul., 1998 | JP.
| |
Primary Examiner: Schilling; Richard L.
Attorney, Agent or Firm: Pillsbury Madison & Sutro LLP
Claims
What is claimed is:
1. A process for making a lithographic printing plate which comprises
subjecting a lithographic printing plate precursor having at least a
hydrophilic layer on a support and a silver thin layer on said hydrophilic
layer to exposure by a laser beam thereby imagewisely removing said silver
thin layer and exposing said hydrophilic layer, wherein the hydrophilic
layer adjacent to said silver thin layer contains at least one inorganic
oxide in particulate form, having a particle size of 0.001 to 0.1 .mu.m.
2. The process for making a lithographic printing plate according to claim
1, wherein the inorganic oxide is at least one of an oxide of elements
selected from the group consisting of aluminum, silicon, zirconium and
titanium.
3. The process for making a lithographic printing plate according to claim
1, wherein imaging is carried out by using a laser having an output power
on said lithographic printing plate precursor of 0.1 to 10 W, and a silver
amount in said silver thin layer is 0.1 to 1.5 g/m.sup.2.
4. The process for making a lithographic printing plate according to claim
1, wherein the silver thin layer comprises a physical development silver
formed by the silver complex diffusion transfer process.
5. The process for making a lithographic printing plate according to claim
4, wherein the silver thin layer is formed by providing a hydrophilic
physical development nuclei layer containing an oxide of at least one
element selected from the group consisting of aluminum, silicon, zirconium
and titanium, and a silver halide emulsion layer on a support in this
order, subjecting to developing treatment by the silver complex diffusion
transfer process without effecting exposure, and subjecting to wash-off
the silver halide emulsion layer.
6. The process for making a lithographic printing plate according to claim
1, wherein the inorganic oxide in said hydrophilic layer is contained in
an amount of 50% by weight or more.
7. The process for making a lithographic printing plate according to claim
1, wherein the silver thin layer is constituted by granular silver
particles having an average particle size of 0.005 to 0.2 .mu.m.
8. The process for making a lithographic printing plate according to claim
7, wherein said granular silver particles are formed in the presence of a
silver halide solvent.
9. The process for making a lithographic printing plate according to claim
8, wherein said silver halide solvent is an amine compound.
10. The process for making a lithographic printing plate according to claim
9, wherein said amine compound is a compound represented by the formula
(I):
##STR9##
wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5
represents a substituted or unsubstituted amino group; and the remaining
substituents each represent a hydrogen atom, a halogen atom, a substituted
or unsubstituted saturated or unsaturated alkyl group, cycloalkyl group,
alkoxy group, aryl group, acyl group, aroyl group or heterocyclic group,
or adjacent two of these substituents may form a ring.
11. The process for making a lithographic printing plate according to claim
1, wherein a second hydrophilic layer of polymer having a thickness of
0.01 to 0.5 .mu.m is further provided on said silver thin layer.
12. The process for making a lithographic printing plate according to claim
11, wherein said second hydrophilic layer contains 1 to 30% by weight of a
hydrophobic compound.
13. The process for making a lithographic printing plate according to claim
12, wherein said hydrophobic compound is a compound having a mercapto
group and at least one of a hydrophobic substituent.
14. The process for making a lithographic printing plate according to claim
1, wherein UV exposure is carried out after exposing said hydrophilic
layer.
15. The process for making a lithographic printing plate according to claim
1, wherein UV exposure is carried out to the lithographic printing plate
precursor after laser beam exposure and before initiation of printing.
16. The process for making a lithographic printing plate according to claim
1, wherein UV exposure is carried out to the lithographic printing plate
precursor during laser beam exposure.
17. The process for making a lithographic printing plate according to claim
1, wherein the support is a film or a polyethylene-coated paper.
Description
BACKGROUND OF THE INVENTION
This invention relates to a process for making a lithographic printing
plate, more specifically to a process for making a lithographic printing
plate which can be handled under a room light, can image with a laser
under heat-mode, can provide an image with high resolution and generates
no waste liquid by the plate-making method of a lithographic printing
material.
A lithographic printing plate comprises an oleophilic image area which
accepts oily ink, and an oil-repellent non-image area which does not
accept ink. The non-image area generally comprises a hydrophilic portion
which accepts water. In a usual lithographic printing plate, printing is
carried out by supplying both of water and an ink to a plate surface
whereby the image area selectively accepts the ink and the non-image area
selectively accepts water, and transferring the ink on the image area to a
material to be printed such as paper, or the like.
A lithographic printing plate has now been prepared by forming an
oleophilic ink receptive layer on a substrate such as an aluminum plate, a
zinc plate, paper or the like, the surface of which are subjected to
hydrophilic treatment. Among these, it is general to use those in which a
photosensitive material such as a diazo compound or a photopolymer, etc.
is provided on an aluminum base the surface of which is subjected to
hydrophilic treatment which is so-called a presensitized (PS) plate, or
those in which an image is formed by utilizing a silver complex diffusion
transfer process (the DTR method) using a silver halide on paper or a
plastic support as a photosensitive material.
A method for forming an ink receptive layer (hereinafter referred to as "an
image layer") by a diazo compound or a photopolymer comprises firstly
coating a photosensitive material such as a diazo compound, a photopolymer
or the like on a substrate such as a metal plate, paper, a laminated
plate, an insulating substrate, or the like. Then, light is exposed to the
photosensitive material to cause chemical change whereby dissolution
properties to a developing solution are changed. Here, the photosensitive
material can be divided into two types depending on the kind of the
chemical change. That is, one is a negative type in which the portion to
which light is exposed is polymerized and cured to become insoluble to a
developing solution, and the others is a positive type in which a
functional group at the portion to which light is exposed is changed to
have solubility in a developing solution. In either of the case, the
photosensitive material insoluble in a developing solution, which remains
on the substrate after processing with a developing solution, becomes an
image layer.
On the other hand, a lithographic printing plate using the DTR method,
particularly a lithographic printing plate having a physical development
nuclei layer on a silver halide emulsion layer is described in, for
example, U.S. Pat. Nos. 3,728,114, No. 4,134,769, No. 4,160,670, No.
4,336,321, No. 4,501,811, No. 4,510,228 and No. 4,621,041. Exposed silver
halide microcrystals cause chemical development by the DTR developer and
change to black silver to form a hydrophilic non-image area. On the other
hand, unexposed silver halide microcrystals become silver complex by a
complexing agent in a developing solution to diffuse to a physical
development nuclei layer at the surface thereof and cause physical
development in the presence of a nucleus whereby an image area mainly
comprising ink receptive physically developed silver is formed. Also, a
lithographic printing plate in which a physical development nuclei layer
and a silver halide emulsion layer are coated in this order on a grained
and anodized aluminum support is disclosed in, for example, Japanese
Provisional Patent Publications No. 260491/1988, No. 116151/1991, No.
282295/1992 or the like. The above-mentioned lithographic printing plate
is imagewisely exposed, followed by DTR development, the silver halide
emulsion layer is washed with warm water to form an image area mainly
comprising the physically developed silver on the anodized aluminum base.
As a plate-making step of the process for making these printing plates, in
the past, it was a main stream to prepare an intermediate film or a block
copy from letters, images or photographic copies, gathering these to a
plate to prepare a finishing film and then to use close contact exposure
system with an ultraviolet ray or a white light. Also, a method of
laminating block copies to prepare a complete block copy and photographing
it with a camera for plate making has been used. However, accompanying
with the progress of computer technology, it has been employed a laser
direct imaging system in which digital signal from computer information is
transferred to an exposure device (computer to plate) and a photosensitive
material is directly exposed by using a laser. The laser direct imaging
system has advantages of low cost, time-saving, high productivity in many
kinds of products with a small size or the like since films to be used in
the course of the processing can be omitted.
In order to be applied with the laser direct imaging system, a
photosensitive material having a high sensitivity is preferably used. In a
diazo compound or a photopolymer, their sensitivities are low as several
to several hundreds mJ/cm.sup.2 since a photochemical reaction occurs.
Thus, to use the material for exposure, a laser output apparatus is
required to be high power output whereby there are problems that the
apparatus becomes large or a cost becomes expensive.
On the other hand, when an image is formed by the DTR method using a silver
halide, its sensitivity is several .mu.J/cm.sup.2 so that exposure can be
carried out sufficiently with a simple and easy semiconductor laser or the
like. However, there is a defect that efficiency and plate-making
operations become markedly poor since storage, coating to a substrate or
the like before subjecting to exposure must be carried out under a safety
light. Further, in the case of the diazo compound or the photopolymer, the
reaction proceeds by a room light or sunlight and their reactivities
change at a high temperature. Moreover, when an oxygen is present, it
becomes an inhibitor of the reaction. Thus, it is necessary to treat under
a dark room or store at a low oxygen condition until exposure and
development are carried out.
Furthermore, in the above image formation methods, it is general to carry
out processing with a liquid using a developing solution so that there is
a defect that treatment of the waste solution becomes environmental issue.
From 1995, a waste liquid is prohibited to throw into the ocean and
processing with a dried state is earnestly desired today.
As a material which satisfies the above demand, it has been proposed a
printing plate of a system in which image formation is carried out by
providing an oleophilic metal thin layer on a support having a hydrophilic
surface and imagewisely removing the oleophilic metal thin layer with
irradiation of a high output heat-mode laser beam. For example, in
Japanese Provisional Patent Publication No. 180976/1998, it is disclosed a
process for making a plate by effecting a heat-mode laser exposure of a
printing plate precursor in which a silver thin layer is formed on a
support having a hydrophilic layer by DTR development without effecting
development.
For making such a printing plate precursor, the silver complex diffusion
transfer process is effective as a method for forming a silver thin film
on a support. As the first system, there is a system in which a material
wherein a physical development nuclei layer is provided on a support and a
material wherein a silver halide emulsion layer is coated on a support as
a donor for a silver complex salt are passed through a physical developer,
piled up and subjecting to diffusion transfer development to precipitate
silver on physical development nuclei to form a silver thin layer.
Examples of the material using the system of forming a silver thin film as
mentioned above may include Copy rapid (trade name, available from Agfa
Gevaert) or the like.
As the second system, a material, in which a silver halide emulsion layer
is provided as a donor for the silver complex salt on a support to which a
physical development nuclei layer is provided, is subjected to physical
development processing, and then, the silver halide emulsion layer is
washed-off to form a silver thin film on the physical development nuclei.
Examples of employing such a system to form a silver thin film may include
Silver Digiplate SDP-.alpha.R (trade name, available from Mitsubishi Paper
Mills Ltd.), Silverlith SDB (trade name, available from E.I. Du Pont) or
the like.
However, according to the above two-types of the systems, there are
problems that preparation of the silver halide emulsion layer is
troublesome, preparation of the silver thin film requires dark room and
the like.
As the third system, a support to which a physical development nuclei layer
is provided is immersed in a solution containing a silver complex salt
dissolved by a silver halide solvent, and a reducing agent, to form a
silver thin layer on the physical development nuclei. This system has been
also known as the electroless plating system, and disclosed in, for
example, Japanese Patent Publications No. 23745/1967 and No. 12862/1968,
and Japanese Provisional Patent Publication No. 287542/1993.
However, according to these methods disclosed in the prior art references,
there are drawbacks that desired printability cannot be obtained, a silver
film is required to be formed within a shorter time and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for making a
lithographic printing plate which can handle under a room light, is
suitable for a direct imaging method by a laser beam, can provide an image
with high resolution and generates no waste liquid by the plate-making
method of a lithographic printing material.
Another object of the present invention is to provide a process for making
a lithographic printing plate in which an ink/water response is improved
when a film or a polyethylene-coated paper is used as a support.
The present inventors have intensively studied to overcome the
above-mentioned problems, and as a result, they have found the following
invention.
The process for making a lithographic printing plate of the present
invention comprises subjecting a lithographic printing plate precursor
having at least a hydrophilic layer on a support and a silver thin layer
on said hydrophilic layer to exposure by a laser beam whereby imagewisely
removing said silver thin layer and exposing said hydrophilic layer,
wherein the hydrophilic layer adjacent to said silver thin layer contains
at least one inorganic oxide.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the present invention, the silver thin layer area is hydrophobic, and
the hydrophilic layer exposed area is hydrophilic as a matter of course.
Thus, due to the presence or absence of heat-mode exposure, difference
occurs on the surface of the lithographic printing plate as an
ink-receptive area and an ink-repellent (water-acceptance) area. That is,
when a plate is prepared according to the process for making a
lithographic printing plate of the present invention, the silver thin
layer heated by the laser beam exposure is thermally fused or melted to
become fine particles (and thereafter these fine particles are removed by
using a removing apparatus, if necessary), whereby the hydrophilic layer
thereunder exposed to become a non-image portion which repels an ink but
accepts water. On the other hand, at the portion which is not heated, the
silver thin layer remains so that it becomes an image portion which
accepts ink whereby lithographic printing can be carried out.
However, accompanying with heat fusion of the silver thin layer by the
laser beam exposure, at the neighbor of the surface of the hydrophilic
layer adjacent to the silver thin layer is also heated to a high
temperature. Thus, if the heat resistance of the material constituting the
surface of the hydrophilic layer is poor, the surface characteristics of
the hydrophilic layer possessed by the layer before exposure are changed
by heating whereby stain at printing is likely induced.
Also, even if there is no apparent change in hydrophilicity of the
hydrophilic layer, if the hydrophilic layer is deteriorated by high
temperature heating and is likely peeled off from a support, stain at
printing is likely caused when the support is a film or
polyethylene-coated paper since the support surface does not essentially
have hydrophilicity which can endure printing.
In this point, an inorganic oxide generally has heat resistance and thus,
it is thermally extremely stable. Thus, by adding the inorganic oxide to
the hydrophilic layer, change in characteristics at printing can be
prevented.
Among the present invention, in a process for making a lithographic
printing plate of the second invention, the inorganic oxide is at least
one of an oxide of elements selected from the group consisting of
aluminum, silicon, zirconium and titanium.
By adding an oxide of these elements to the hydrophilic layer, thermal
change of the hydrophilic layer can be prevented, and according to the
hydrophilic properties possessed by these inorganic oxides, excellent
ink/water responses can be provided to the lithographic printing plate at
printing.
Among the present invention, in a process for making a lithographic
printing plate of the third invention, the particle size of said inorganic
oxide is 0.001 to 0.1 .mu.m.
If the particle size is greater than 0.1 .mu.m, it is difficult to form a
uniform film at the area adjacent to the silver thin layer, and
consequently there cause an area which is easily removable and an area
which is difficultly removable in the silver thin layer at exposure to
laser whereby unevenness occurs in removability.
By using an inorganic oxide having a particle size of 0.001 to 0.1 .mu.m. a
uniform and firm film can be formed as the hydrophilic layer whereby
thermal loss can be uniformly prevented over the whole hydrophilic layer
and removability of the silver thin layer can be made uniform. According
to this, an image having high resolution can be obtained.
Among the present invention, in a process for making a lithographic
printing plate of the fourth invention, the silver thin layer of said
lithographic printing plate precursor comprises a physical development
silver formed by the silver complex diffusion transfer process.
The silver thin layer which is physically developed by the silver complex
diffusion transfer process has higher laser absorption ratio and
hydrophilicity as compared with the silver thin layer formed by the
deposition method, etc., whereby removal efficiency of the silver thin
film by laser beam exposure is improved and an ink receptivity of the
image area silver thin film becomes high so that the characteristics as
the lithographic printing plate are improved.
Among the present invention, in a process for making a lithographic
printing plate of the fifth invention, the silver thin layer is formed by
providing a hydrophilic physical development nuclei layer containing an
oxide of at least one element selected from the group consisting of
aluminum, silicon, zirconium and titanium, and at least one of silver
halide emulsion layer on a support in this order, subjecting to developing
treatment by the silver complex diffusion transfer process without
effecting exposure, and subjecting to wash-off the silver halide emulsion
layer to form a physical development silver on the physical development
nuclei in a layered state.
In such a layer constitution, the physical development nuclei layer also
acts as the above-mentioned hydrophilic layer, and a hydrophilic layer
containing an inorganic oxide may be further provided between the physical
development nuclei layer and the support.
In this method, hydrophilicity of the exposed surface can be markedly
improved and excellent ink/water response can be obtained. Detailed
mechanism thereof has not yet been clear but it can be considered that the
silver thin film and an oxide of the above element which is an inorganic
oxide exist extremely close to each other and the ratio of such a
configuration becomes large whereby thermal damage of the hydrophilic
layer becomes little.
Among the present invention, in a process for making a lithographic
printing plate of the sixth invention, the inorganic oxide in said
hydrophilic layer is contained in an amount of 50% by weight or more.
Accompanying with increase in the content of the inorganic oxide in the
hydrophilic layer, the ratio of extremely closely existing ratio of the
silver thin layer and the inorganic oxide increases. When the weight ratio
of the inorganic oxide becomes 50% or more, thermal change in the
hydrophilic layer can be markedly controlled and more excellent ink/water
response at the time of initiating printing can be obtained.
Among the present invention, in a process for making a lithographic
printing plate of the seventh invention, the silver thin layer is
constituted by granular silver particles having an average particle size
of 0.005 to 0.2 .mu.m.
The silver thin layer comprising such silver particles can be easily
removed by a heat mode laser exposure and printability is also excellent.
Among the present invention, in a process for making a lithographic
printing plate of the eighth invention, said granular silver particles are
formed in the presence of a silver halide solvent.
The silver thin layer thus prepared has excellent ink receptivity.
Among the present invention, in a process for making a lithographic
printing plate of the ninth invention, said silver halide solvent is an
amine compound.
The silver thin layer thus prepared has more excellent ink receptivity.
Among the present invention, in a process for making a lithographic
printing plate of the tenth invention, said amine compound is a compound
represented by the formula (I):
##STR1##
wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5
represents a substituted or unsubstituted amino group; and the remaining
substituents each represent a hydrogen atom, a halogen atom, a substituted
or unsubstituted saturated or unsaturated alkyl group, cycloalkyl group,
alkoxy group, aryl group, acyl group, aroyl group or heterocyclic group,
or adjacent two of these substituents may form a ring.
Among the present invention, in a process for making a lithographic
printing plate of the eleventh invention, a hydrophilic polymer layer
having a thickness of 0.01 to 0.5 .mu.m is further provided on said silver
thin layer of the lithographic printing plate.
The hydrophilic polymer layer has a role of preventing deterioration in
sensitivity accompanied by modification of the silver thin layer surface
with a lapse of time. Also, whereas the hydrophilic polymer has light
transmittance at the infrared spectral region, when a hydrophilic polymer
layer is present on the silver thin layer, it causes a bad effect on the
removal sensitivity of the silver thin layer. However, when the thickness
of the hydrophilic polymer layer is within the above range, the
sensitivity is substantially not lowered.
Among the present invention, in a process for making a lithographic
printing plate of the twelfth invention, said hydrophilic polymer layer
contains 1 to 30% by weight of a hydrophobic compound.
When the content of the hydrophobic compound in the hydrophilic polymer
layer is within the above range, ink acceptability can be improved without
substantially impairing removal efficiency of the silver thin layer.
Among the present invention, in a process for making a lithographic
printing plate of the thirteenth invention, said hydrophobic compound is a
compound having a mercapto group and at least one of a hydrophobic
substituent.
If the hydrophobic compound is a compound having a mercapto group and at
least one of a hydrophobic substituent, it has an interaction with the
silver thin layer surface whereby ink acceptability can be improved and
stabilized.
Among the present invention, in a process for making a lithographic
printing plate of the fourteenth invention, after exposing the hydrophilic
layer by laser beam exposure, i.e., after laser beam exposure, and, if
desired, further removing the silver thin layer residue remained on the
hydrophilic layer, UV exposure is carried out at least on the hydrophilic
layer.
Among the inorganic oxides, there is a substance which can control the
surface characteristics, particularly hydrophilic/hydrophobic
characteristics by UV exposure. Thus, by carrying out UV exposure to the
hydrophilic layer containing such an inorganic oxide, a contact angle of
the hydrophilic layer can be lowered whereby good printed material with
less printing stain can be obtained.
Among the present invention, in a process for making a lithographic
printing plate of the fifteenth invention, UV exposure is carried out to
the lithographic printing plate precursor during after laser beam exposure
and before initiation of printing.
By effecting UV exposure during after laser beam exposure and before
initiation of printing, hydrophilicity of the hydrophilic layer which is
an non-image area can be improved without lowering adhesiveness of the
silver thin layer which is an image area.
Among the present invention, in a process for making a lithographic
printing plate of the sixteenth invention, UV exposure is carried out to
the lithographic printing plate precursor during laser beam exposure.
By effecting UV exposure during laser beam exposure, the hydrophilic layer
exposed by laser beam exposure is then exposed to UV rays whereby
hydrophilicity of the hydrophilic layer which is a non-image area can be
improved without elongating the total plate-making time.
Among the present invention, in a process for making a lithographic
printing plate of the seventeenth invention, as the support for the
lithographic printing plate precursor of the present invention, a film or
a polyethylene-coated paper is used.
A film or a polyethylene-coated paper is inexpensive than an aluminum base
but inferior in hydrophilicity at the surface thereof than the aluminum
base in which the surface treatment is carried out to make the surface
hydrophilic. Thus, it was inferior in various printability including an
ink/water response. However, even when a film or a polyethylene-coated
paper is used as a support, hydrophilicity at the non-image area is
improved by providing a hydrophilic layer containing an inorganic oxide,
and an ink/water response corresponding to the aluminum base in which the
surface treatment is carried out to make the surface hydrophilic can be
obtained. Moreover, the inorganic oxide can improve physical strength of
the hydrophilic layer so that runlength is also improved.
Among the present invention, in a process for making a lithographic
printing plate of the eighteenth invention, imaging is carried out by
using a laser having an output power on said lithographic printing plate
precursor of 0.1 to 10 W, and a silver amount in said silver thin layer is
0.1 to 1.5 g/m.sup.2.
An amount of silver in the silver thin layer markedly affects on the
removability of the silver thin film at imaging laser and print ability at
the time of printing. If an amount of silver in the silver thin layer is
larger than 1.5 g/m.sup.2, removability at imaging becomes poor, and
silver remains on the surface of the hydrophilic surface, as a result,
stain at printing is induced. On the other hand, if the amount of silver
in the silver thin layer is less than 0.1 g/m.sup.2, removability is
improved and the hydrophilic surface is exposed, but runlength becomes
worse at printing. Thus, by making the silver amount in the silver thin
layer 0.1 to 1.5 g/m.sup.2, a lithographic printing plate in which both of
removability and printability at imaging are well balanced and both
excellent can be prepared.
According to the present invention, by heating the area which becomes a
non-image area by a laser beam in accordance with the desired images to be
prepared, a lithographic printing plate can be prepared without using a
liquid developer or a devices to be used for subjecting to these
treatments. Moreover, operations under light room can be carried out
during the plate-making step from the lithographic printing plate
precursor and the printing step can be realized, and long term
preservation under light room or oxygen becomes possible stably.
The lithographic printing plate precursor according to the present
invention has at least one hydrophilic layer on a support, and a silver
thin layer is further provided thereon. As the process for making a
lithographic printing plate of the present invention, irradiation with a
laser beam is imagewisely carried out to the lithographic printing plate
(non-image portion exposure). Here, the silver thin layer is removed
(ablation) by laser beam exposure, or after laser beam exposure, a residue
remained at the exposed portion of the printing plate precursor is removed
by a means such as vacuum evacuation, or the like, or else, silver
particles are granulated, making a plate is completed by finally exposing
the hydrophilic layer at the area which becomes non-image area.
Thereafter, when it is mounted on a lithographic printer, ink is accepted
by the area of the remaining silver thin layer and water is accepted by
the exposed hydrophilic layer whereby printing can be carried out.
The hydrophilic layer according to the lithographic printing plate of the
present invention contains at least one of inorganic oxides.
In the present invention, the inorganic oxide means a compound in which it
has at least an area which directly bonds to oxygen, and in addition to an
oxide, it represents a hydroxide, hydrated oxide, and a complex compound
thereof. As the elemental component of such an inorganic oxide, there may
be mentioned aluminum, silicon, zirconium, titanium, beryllium, zinc,
iron, tin, barium, silver, strontium, bismuth, tungsten, etc. In the
inorganic oxide according to the present invention, it may contain at
least one of these elements and those which contain two or more kinds
thereof such as alumina silicate, etc. are also included. Specific
examples of such inorganic oxide may include, for example, inorganic
oxides such as aluminum oxide, silicon dioxide, zirconium oxide, titanium
dioxide, beryllium oxide, zinc oxide, iron oxide, tin oxide, barium oxide,
silver oxide, strontium oxide, bismuth oxide and tungsten oxide; inorganic
hydroxides such as aluminum hydroxide, silicon hydroxide, zirconium
hydroxide, titanium hydroxide, beryllium hydroxide, zinc hydroxide, iron
hydroxide, tin hydroxide, barium hydroxide, silver hydroxide, strontium
hydroxide, bismuth hydroxide and tungsten hydroxide; hydrated inorganic
oxides of the above mentioned inorganic oxides; and a composite compound
thereof.
These inorganic oxides according to the present invention used in the form
of fine particles preferably, are excellent in heat resistance and
difficult to dissolve in a solvent of an ink and a fountain solution.
Preferred particle size of the inorganic oxide according to the present
invention is 0.001 to 0.1 .mu.m, more preferably 0.005 to 0.05 .mu.m.
Also, in the conventional silver salt printing plate using a film or a
paper based support, improvement in runlength or hydrophilicity is carried
out by using an inorganic oxide such as silicon dioxide or titanium
dioxide having a relatively large particle size such as 0.1 to 10 .mu.m to
make unevenness on the surface of the hydrophilic layer, these inorganic
oxides may be used in combination with the inorganic oxides of the present
invention.
Among these inorganic oxides, in view of hydrophilicity and an ink/water
response at printing, at least one oxide of an element selected from the
group consisting of aluminum, silicon, zirconium and titanium is
particularly preferred. In the present invention, an inorganic oxide is
used in the form of a dispersant, as such a dispersant, alumina sol,
colloidal silica, titania sol and zirconia sol are preferably used. These
sols may be an aqueous sol or may be an organo sol using an organic
solvent. These materials may be used singly or in combination of two or
more kinds having different compositions, grain sizes, etc.
The inorganic oxide according to the present invention may be subjected to
surface-modification treatment with a suitable surface modifier to improve
ionic property or dispersibility. As the surface modifier, there may be
used, for example, various kinds of ionic species, various kinds of
surfactants, and coupling agents containing silicon, titanium, aluminum,
etc. Moreover, as the dispersibility stabilizer, a cation derived from an
alkali metal or ammonium, etc., or an anion derived from acetic acid,
hydrochloric acid, nitric acid, sulfuric acid, etc. may be contained.
When the inorganic oxide according to the present invention forms a film
itself, or forms an inorganic oxide film having runlength in combination
with a hardening agent, if desired, then the hydrophilic layer according
to the present invention may comprise an inorganic oxide. Also, in the
hydrophilic layer according to the present invention, a hydrophilic
polymer, etc. may be used in combination. When the hydrophilic polymer,
etc. is used, a weight ratio (content) of the inorganic oxide in the
hydrophilic layer according to the present invention is preferably 50% by
weight or more. The thus prepared hydrophilic layer can markedly control
thermal changes of the hydrophilic layer by laser beam exposure, and not
only excellent in stain resistance at printing but also excellent
ink/water response. More preferred content of the inorganic oxide is 70%
by weight or more, further preferably 80% by weight or more.
As the hydrophilic polymer to be used in the hydrophilic layer according to
the present invention, the following examples may be mentioned. These
materials may be used in combination of two or more kinds in view of
printabilities such as background stain or runlength.
As the natural materials, there may be mentioned those obtained from algae
such as starches, marine algae mannan, agar and sodium alginate; vegetable
viscose material such as mannan, pectin, tragacanth gum, Karaya gum,
xanthine gum, guiac bean gum, Locust bean gum and gum arabic;
microorganism viscose materials including homopolysaccharides such as
dextran, glucan, xanthane gum and levan; and heteropolysaccharides such as
succinoglucan, pullulan, Curdlan and xanthane gum; proteins such as glue,
gelatin, casein and collagen; chitin and derivatives thereof, and the
like.
Also, as the semi-natural (semi-synthesized) materials, there may be
mentioned modified gums such as cellulose derivatives, and carboxymethyl
guiac bean gum; modified starches including roasted starches such as
dextrin; oxidized starches, esterified starches, and the like.
As the synthesized materials, there may be mentioned polyvinyl alcohol,
modified polyvinyl alcohols such as partially acetalized polyvinyl
alcohol, allyl-modified polyvinyl alcohol, polyvinyl methyl ether,
polyvinyl ethyl ether, polyvinyl isobutyl ether, etc; polyacrylic acid
derivatives and polymethacrylic acid derivatives such as polyacrylic acid
salts, partially saponified product of polyacrylates, polymethacrylic acid
salts, and polyacrylamides; polyethylene glycol, polyethylene oxide,
polyvinyl pyrrolidone, vinyl pyrrolidone/vinyl acetate copolymer, carboxy
vinyl polymerized material, styrene/maleic acid copolymer,
styrene/crotonic acid copolymer, and the like.
Among these, for forming the silver thin film by the silver complex
diffusion transfer process, when the hydrophilic layer is used also as a
silver halide emulsion layer, gelatin is preferably used.
As the gelatin to be used in the hydrophilic layer according to the present
invention, any gelatin which is prepared from animal collagen as a
starting material can be used, but preferably gelatin which is prepared
from collagen obtained from pigskin, cattle skin, and cattle bone. Also,
there is no specific limitation about the kind of gelatin, but in addition
to lime-treated gelatin and acid-treated gelatin, gelatin derivatives as
disclosed in Japanese Patent Publications No. 4854/1963, No. 5514/1964,
No. 12237/1965 and No. 26345/1967; U.S. Pat. Nos. 2,525,753, No.
2,594,293, No. 2,594,293, No. 2,614,928, No. 2,763,639, No. 3,118,766, No.
3,132,945, No. 3,186,846, No. 3,312,553, and British Patent No. 1,033,189.
These materials may be used singly or in combination of two or more.
When gelatin is used as a hydrophilic layer, it can be cured by a gelatin
curing agent. As the gelatin curing agent, there may be mentioned, for
example, inorganic compounds such as chromium alum; aldehydes such as
formalin, glyoxal, malealdehyde and glutaraldehyde; N-methylal compounds
such as urea, ethylene urea, etc.; aldehyde analogue compounds such as
mucochloric acid and 2,3-dihydroxy-1,4-dioxane; compounds having an active
halogen such as 2,4-dichloro-6-hydroxy-S-triazine salt and
2,4-dihydroxy-6-chloro-S-triazine salt: divinyl sulfone, divinyl ketone,
N,N,N-triacryloylhexahydrotriazine, compounds having an ethyleneimino
group which is an active three-membered ring or at least two epoxy groups
in the molecule, and dialdehyde starches as a polymer hardening agent, or
the like, and these compounds may be used singly or in combination of two
or more.
Also, the hydrophilic layer according to the present invention can be
formed by dissolving or dispersing a hydrophilic layer constituting
composition in a suitable solvent, and coating it onto a support which is
used as a lithographic printing plate precursor, followed by drying. To
prepare a coating solution for forming a hydrophilic layer well, or to
improve coating property, at least one of an anionic, cationic or nonionic
surfactant may be used as a coating aid, and a matte agent, a thickening
agent or an antistatic agent may also be used in combination.
The silver thin layer according to the present invention can be formed by a
generally known means for forming a metal thin film such as vacuum
deposition, sputtering, CVD (Chemical Vapor Deposition), plating, etc. On
the other hand, the silver thin layer can be formed by using the method of
physical development using the silver complex salt diffusion transfer
process. In this method, when it is used as a printing plate, not only
pure metal silver but also so-called lipophilic contaminants such as
oxides, sulfide, etc. are mixedly present in the silver thin layer which
becomes an image area, and surface unevenness is suitably formed in
microscopic view whereas it is a continuous film. Thus, adsorption of ink
prepared by this method becomes better than those prepared by other
methods, and a laser absorption ratio becomes high and sensitivity as the
lithographic printing material is also increased. Moreover, it is
preferred in the point that industrial mass production can be easily
carried out.
In the present invention, a silver thin layer comprising silver particles
having an average particle size of 0.005 to 0.2 .mu.m is preferably used.
The silver thin layer comprising such silver particles is easily removed
by exposure using a heat-mode laser beam and its printability is also
excellent. In the silver thin layer comprising silver particles having an
average particle size of more than 0.2 .mu.m or the silver thin layer
comprising silver particles having an average particle size of less than
0.005 .mu.m prepared by vacuum deposition, ink acceptability of the silver
thin layer is poor so that image quality of the printed matter becomes
also poor.
In the present invention, three types of systems of the silver complex
diffusion transfer processes have been known as preferred methods for
preparing a silver thin layer. Among these three types of systems, the
first two systems have been practically used in a plate making camera or a
photo-mode laser exposing machine. Printability of the silver thin layer
formed by these methods depends on plate-constituting elements such as the
layer constitution of a plate, a halogen composition of a silver halide
emulsion, an average particle size of emulsion particles, a development
inhibitor or the like; elements for constituting a diffusion transfer
development solution such as a developing agent, a silver halide emulsion,
a development inhibitor or the like; and conditions of the diffusion
transfer development processing. As for these factors, there are
disclosed, for example, in U.S. Pat. Nos. 3,728,114, No. 4,134,769, No.
4,160,670, No. 4,336,321, No. 4,501,811, No. 4,510,228 and No. 4,621,041,
Japanese Provisional Patent Publications No. 260491/1988, No. 116151/1991
and No. 282295/1992 or the like. For controlling the silver particles
constituting the silver thin layer to 0.005 to 0.2 .mu.m, it can be
accomplished by optimizing these known techniques.
As for the third system, it is disclosed in Japanese Patent Applications
No. 304390/1997, No. 304391/1997, No. 304392/1997, No. 304393/1997 and No.
304394/1997, and by optimizing the composition of the processing solution
constituted by a developing agent, a silver halide solvent, silver salt,
etc. according to the techniques disclosed therein, silver particles
constituting the silver thin layer can be controlled to 0.005 to 0.2 .mu.m
whereby preferred printability can be obtained.
As a method for measuring the particle size of silver particles
constituting a silver thin layer, there may be mentioned a method in which
the silver thin layer is photographed and the sizes of the respective
silver particles in the photograph are measured, and an average value is
calculated therefrom. As a simple and easy method, mean-sized particles
are picked up and the sizes of these particles may be measured.
In the present invention, it is preferred to use physical development
nuclei for preparing a good silver thin film at the time of preparation.
As the physical development nuclei, there may be mentioned a metal colloid
fine particle of silver, antimony, bismuth, cadmium, cobalt, lead, nickel,
palladium, rhodium, gold, platinum, or the like, or a sulfide, a
polysulfide, a selenide of these metals, or a mixture thereof, or a mixed
crystal thereof.
For forming a layer by previously coating physical development nuclei, a
hydrophilic polymer may be used in combination with the physical
development nuclei. As the hydrophilic polymer to be used in the physical
development nuclei layer, there may be mentioned, for example, gelatin,
starch, dialdehyde starch, carboxymethyl cellulose, gum arabic, sodium
alginate, hydroxyethyl cellulose, polystyrenesulfonic acid, sodium
polyacrylate, a copolymer of vinylimidazole and acrylamide, a copolymer of
acrylic acid and acrylamide, a hydrophilic polymer such as polyvinyl
alcohol or the like, or an oligomer thereof, and a content thereof is
preferably 0.5 g/m.sup.2 or less.
To the physical development nuclei layer, a developing agent such as
hydroquinone, methyl hydroquinone, catechol, etc., or a known
film-hardening agent such as formalin, dichloro-s-triazine, etc. may be
further added. Also, in the preferred embodiment of the present invention,
at least one of an oxide of an element selected from the group consisting
of aluminum, silicon, zirconium and titanium is added to the physical
development nuclei layer. These oxides may be the same as those used in
the hydrophilic layer according to the present invention.
Also, when a silver halide emulsion layer is provided as a donor of a
silver ion for forming a silver thin layer, silver halide such as silver
chloride, silver bromide, silver chlorobromide, and silver iodide may be
used, and they are used in the form of a crystal. The silver halide
crystal may contain a heavy metal salt such as rhodium salt, iridium salt,
palladium salt, ruthenium salt, nickel salt, platinum salt, etc., and an
amount thereof is 10.sup.-8 to 10.sup.-3 mole per mole of silver halide.
Crystal form of the silver halide is not particularly limited, and it may
be cubic or tetradecahedral particles, and further core-shell type or
tabular particles. The silver halide crystal may be monodispersed or
polydispersed crystals and the average particle size thereof is within the
range of 0.2 to 0.8 .mu.m. As one of the preferred examples, there maybe
mentioned a monodispersed or polydispersed crystals containing 80 mole %
or more of silver chloride containing a rhodium salt or an iridium salt.
Also, when preparation of the silver thin film is carried out by using the
third method, a kind of a silver ion is not particularly limited, but it
is selected from silver nitrite and silver halide such as silver chloride,
silver bromide, silver iodide, silver chlorobromide, silver chloroiodide,
silver chlorobromoiodide, and the like.
In the present invention, as a reducing agent to be used for preparing the
silver thin film, there may be used hydroquinone, phenylenediamine,
phenidone, dimethylphenidone, and the like.
A development processing solution for forming a silver thin layer may
contain an alkaline substance for adjusting pH such as sodium hydroxide,
potassium hydroxide, lithium hydroxide, sodium tertiary phosphate, etc.;
or an acidic substance such as sulfuric acid, nitric acid, phosphoric
acid, etc.; a preservative such as a sulfite; a silver halide solvent such
as a thiosulfate, a thiocyanate, a circular imide, 2-mercaptobenzoic acid,
an amine compound, etc; a thickening agent such as hydroxyethyl cellulose,
carboxymethyl cellulose etc; an antifoggant such as potassium bromide; a
development modifier such as a polyoxyethylene compound, an onium compound
etc. Moreover, in the development processing solution, a compound which
improves ink receptivity at the surface of the silver thin film may be
used as disclosed in U.S. Pat. No. 3,776,728.
In the present invention, when a silver thin layer comprising granular
silver particles is to be prepared, it is preferably carried out in the
presence of a compound which becomes a silver halide solvent. The silver
thin layer thus prepared shows excellent ink receptivity. As the silver
halide solvent to be used in the present invention, there may be
mentioned, for example, a sulfite (e.g., anhydrous sodium sulfite,
anhydrous potassium sulfite, etc.), a thiosulfite (e.g., sodium
thiosulfite hexahydrate, ammonium thiosulfite, etc.), and an amine
compound or the like. Among the silver halide solvents as mentioned above,
the amine compound is preferably used in the present invention. The thus
prepared silver thin layer shows more excellent ink receptivity.
In the present invention, the amine compound to be used as a silver halide
solvent may include ammonia and those which are substituted by a
substituted or unsubstituted and saturated or unsaturated alkyl group,
cycloalkyl group, alkoxy group, aryl group, alkanoyl group, aroyl group,
or heterocyclic group, and these substituents may be combined to each
other to form a ring.
In the following, specific examples of the amine compounds are shown, but
the present invention is not limited by them.
______________________________________
A1 NH.sub.3 A2 NH.sub.2 CH.sub.2 CH.sub.3
A3 NH(CH.sub.2 CH.sub.3).sub.2 A4 N(CH.sub.2 CH.sub.3).sub.3
A5 NH.sub.2 CH.sub.2 CH.sub.2 OH A6 NH(CH.sub.2 CH.sub.2 OH).sub.2
A7 N(CH.sub.2 CH.sub.2 OH).sub.3 A8 CH.sub.3
NHCH.sub.2 CH.sub.3
A9 NH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.3 A10 NH.sub.2 CH.sub.2
CH.sub.2 NHCH.sub.2 CH.sub.2 OH
- A11
A12 2##
#STR3##
- A13
##STR4##
______________________________________
Also, in the present invention, a compound represented by the following
formula (I) is more preferred as the amine compound.
##STR5##
wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5
represents a substituted or unsubstituted amino group; and the remaining
substituents each represent a hydrogen atom, a halogen atom, a substituted
or unsubstituted saturated or unsaturated alkyl group, cycloalkyl group,
alkoxy group, aryl group, acyl group, aroyl group or heterocyclic group,
or adjacent two of these substituents may form a ring.
In the compound of the formula (I), when the amino group has a substituent,
said substituent is a substituted or unsubstituted, and a saturated or
unsaturated alkyl group, cycloalkyl group, alkoxy group, aryl group, acyl
group, aroyl group or heterocyclic group, and two of adjacent these
substituents may form a ring by combining with each other. As the halogen
atom, there may be mentioned a chlorine atom, a bromine atom, an iodine
atom or the like.
The above alkyl group may be further substituted by a suitable group (for
example, a halogen atom, an alkoxy group, etc.).
Preferred alkyl group is that having 1 to 10 carbon atoms, more
specifically, a methyl group, an ethyl group, an n-propyl group, an
n-hexyl group, a trichloromethyl group, a vinyl group or the like.
The above cycloalkyl group is a cycloalkyl group having 3 to 10 carbon
atoms or so, and may be further substituted by a suitable group (for
example, an alkyl group, a halogen atom, an alkoxy group, etc.). Specific
examples thereof may include a cyclohexyl group, a cyclopentyl group or
the like.
The above alkoxy group may be a straight or branched one, and may be
further substituted by a suitable group (for example, an alkyl group, a
halogen atom, an alkoxy group, etc.). Preferred alkoxy group is that
having 1 to 10 carbon atoms, more specifically, a methoxy group, an ethoxy
group, an n-propoxy group, an n-hexyloxy group or the like.
As the above aryl group, an aromatic group such as a phenyl group, a
naphthyl group or the like are preferred, and these aromatic groups may be
substituted by a suitable group (for example, a halogen atom, an alkyl
group, an alkoxy group, a nitro group, etc.).
As the above acyl group, a straight or branched acyl group having 1 to 6
carbon atoms may be mentioned, and specific examples thereof are a formyl
group, an acetyl group, a propionyl group, a pivaloyl group or the like.
As an aryl group portion of the above aroyl group, an aromatic group such
as a phenyl group, a naphthyl group or the like are preferably mentioned.
These aromatic groups may be substituted by a suitable group (for example,
a halogen atom, an alkyl group, an alkoxy group, a nitro group, etc.).
As the above heterocyclic group, there may be mentioned, for example, a
substituted or unsubstituted pyridyl group, furyl group, thienyl group or
the like.
Specific examples of the compound represented by the formula (I) are
enumerated below.
##STR6##
These silver halide solvent including the amine compounds as mentioned
above are preferably used in an amount of 0.1 to 100-fold moles, more
preferably 1 to 50-fold moles based on a gram ion number of the silver
ion. These silver halide solvents are used singly or in combination of two
or more.
The silver thin layer after physical development of the lithographic
printing plate precursor according to the present invention is preferably
modify the ink receptive property or strengthen the receptivity thereof by
an optional known surfactant.
Such processing solutions are disclosed, for example in Japanese Patent
Publication No. 29723/1973, U.S. Pat. No. 3,721,559 or the like.
In the present invention, in order to promote removal of the silver thin
layer by laser beam irradiation and to improve efficiency (i.e., it can be
said to be "sensitivity" of the lithographic printing plate precursor of
the present invention) to expose the hydrophilic layer, a light-absorbing
agent which absorbs laser beam may be added either to a support or a
hydrophilic layer. According to this constitution, even if part of the
laser beam transmitted through the silver thin layer, they are absorbed at
the under layer so that thermal efficiency can be improved.
As the light-absorbing agent to be employed for the above object, there may
be mentioned a usual dye or pigment having an absorption region at the
laser beam exposure region, such as carbon black, graphite, copper
sulfide, zinc sulfide, molybdenum trisulfide, black titanium dioxide,
metal-free or metal phthalocyanine, polymethyne series dye (cyanine dye),
azulenium dye, pyrylium, thiopyrylium dye, squarylium series dye,
crocoonium series dye, thiol-nickel complex chlorine dye, mercaptophenol,
mercaptonaphtol complex series dye, triarylmethane series dye, immonium,
diimmonium series dye, anthraquinone series dye, or the like.
In the lithographic printing plate precursor according to the present
invention, a hydrophilic polymer layer may be provided on the silver thin
film. By providing such a hydrophilic polymer layer on the silver thin
film, deterioration in sensitivity of the silver thin layer accompanied by
modification of the surface of the layer with a lapse of time can be
prevented. As the hydrophilic polymer to be used in the hydrophilic
polymer layer, those optionally selected from the above-mentioned
hydrophilic polymers to be used in the hydrophilic layer according to the
present invention may be used. The hydrophilic polymer to be used in the
hydrophilic polymer layer may be the same or different from that used in
the hydrophilic layer, and may be single species or in combination of two
or more kinds.
The thickness of the hydrophilic polymer layer to be provided on the silver
thin film is preferably 0.01 to 0.5 .mu.m. If the thickness of the
hydrophilic polymer layer is less than 0.01 .mu.m, there is little effect
on stain prevention, while if it exceeds 0.5 .mu.m, whereas the
hydrophilic polymer has light transmittance at the infrared spectrum
region, it causes bad effect on removal sensitivity of the silver thin
layer and attachment of ink at the image area sometimes delayed so that it
is not preferred.
In the present invention, it is preferred to add a hydrophobic compound in
the hydrophilic polymer layer in an amount of 1 to 30% by weight based on
the total weight of the hydrophilic polymer layer. If the amount of the
hydrophobic compound in the hydrophilic polymer layer is within the above
range, ink acceptability can be improved without substantially impairing
removal efficiency of the silver thin film. Also, when granular silver
particles having an average particle diameter of 0.005 to 0.2 .mu.m is
used, it can accept ink in itself, but by adding a hydrophobic compound to
the hydrophilic polymer layer, ink acceptability can be stabilized.
As the hydrophobic compound to be used in the present invention, there may
be mentioned, for example, phthalic acid ester such as diethyl phthalate,
dibutyl phthalate, etc.; phosphoric acid ester such as tricresyl
phosphate, etc.; known oils; and various kinds of animal oils and
vegetable oils. Also, mercaptotetrazol derivatives having a hydrophobic
group such as phenylmercaptotetrazole, etc. are also effective, and a
hydrophobic compound having a mercapto group and at least one of a
hydrophobic substituent is suitable. Examples of such a hydrophobic
compounds may include, for example, in addition to the mercaptotetrazole
derivatives such as phenylmercaptotetrazole, etc., a mercaptotriazole
derivative represented by the following formula (II) and a
mercaptoxadiazole derivative represented by the formula (III):
##STR7##
wherein R.sup.6 represents an alkyl group, an aryl group or an aralkyl
group; and R.sup.7 represents a hydrogen atom or an acyl group.
##STR8##
wherein R.sup.6 has the same meaning as defined above.
In the above formula (II), R.sup.6 is preferably an alkyl group having 3 to
16 carbon atoms.
Moreover, as the hydrophobic compound, a compound which gives ink
receptivity is preferably used. Examples thereof are mentioned, for
example, in Japanese Patent Publication No. 29723/1973, U.S. Pat. No.
3,721,559, and these compounds can be used for this purpose.
The hydrophilic polymer layer containing a hydrophobic compound can be
formed, after forming the silver thin layer, by coating a composition for
forming the layer on the silver thin layer. The hydrophobic compounds may
be added to the aqueous hydrophilic polymer solution using a known oil
dispersion technique or after dissolving in a suitable solvent and then
added to the aqueous hydrophilic polymer solution. Also, the compound
having a mercapto group and at least one of a hydrophobic substituent can
be added to the hydrophilic polymer solution by dissolving it using an
amine compound as described in Japanese Provisional Patent Publications
No. 79982/1994 and No. 248630/1995.
Also, in the present invention, after exposing the hydrophilic layer,
simultaneously with laser exposure or after laser exposure, UV exposure
may be carried out at least to the hydrophilic layer. The UV exposure
herein mentioned means irradiating UV rays with a wavelength of 450 nm or
less, preferably about 250 to 390 nm. As a light source for irradiating UV
rays, a mercury lamp or a metal halide lamp can be suitably used.
Inorganic oxides such as TiO.sub.2, ZnO, SnO.sub.2, SrTiO.sub.3, WO.sub.3,
Bi.sub.2 O.sub.3, and Fe.sub.2 O.sub.3 has light absorption at the
ultraviolet rays wavelength region. When these compounds are contained in
the hydrophilic layer, the layer is made more hydrophilic. The mechanism
of promoting the surface hydrophilic is described in detail in Japanese
Provisional Patent Publication No. 140046/1998.
As the support to be used in the lithographic printing plate according to
the present invention, there may be used, for example, paper, various
kinds of films, plastics, paper coated by a resin-like substance, metals,
and a laminate in which a polyester film or paper is laminated to either
of the above-exemplified supports.
Among these, as a support of a film, a polyester film on which an organic
copolymer is coated and a hydrophilic treatment is applied is preferred.
For such a film, a surface treatment may be further carried out to enhance
adhesiveness to the hydrophilic layer, and then a subbing layer comprising
an organic polymer may be provided on the polyester film. As the support,
there may be mentioned the following two types of films.
One of which is to coat a composition comprising an organic solvent which
becomes a swelling agent or a dissolving agent of the polyester film and
an organic copolymer (hereinafter referred to as the "solvent subbing
method"). Examples thereof are mentioned in U.S. Pat. No. 2,830,030;
British Patents No. 772,600, No. 776,157 and No. 785,789; and Japanese
Provisional Patent Publications No. 1718/1975 and No. 8259/1975.
The other is to coat a composition in the form of an aqueous composition
(so-called "latex") of an organic copolymer without substantially
containing an organic solvent (hereinafter referred to as the "aqueous
subbing method"). Examples thereof are mentioned in Japanese Patent
Publications No. 13278/1969 and No. 10988/1970; Japanese Provisional
Patent Publications No. 11118/1974, No. 27918/1976, No. 114670/1977, No.
11177/1979, No. 67745/1980, No. 169145/1983 and No. 77439/1984.
The above-mentioned solvent subbing method involves the problems that
physical properties of the polyester film are deteriorated during subbing
treatment or the organic solvent causes pollution or problems on safety or
hygiene at operation. Thus, the subbing method is transferring to the
aqueous subbing method. Also, for reinforcing adhesion, a support to which
a thin film of gelatin with a coated amount of 0.02 to 0.1 g/m.sup.2 is
provided may be used.
To the surface of the support to be used in the present invention, a
surface treatment may be carried out in order to improve adhesiveness to a
layer coated as an upper layer or solid fine particles may be added to
either of the layers provided on the support.
Also, at the opposite surface (back surface) of the support, which is an
opposite surface to the surface on which the hydrophilic layer, etc.
is/are provided, a layer containing a matte agent or an antistatic agent
may be provided in view of conveyance, etc. in an imaging apparatus, etc.
In the present invention, as a laser to be used for exposing the
hydrophilic layer which contains hydrophilic physical development nuclei
layer by removing the silver thin layer, there may be mentioned a
conventionally known laser including a gas laser such as a carbonic acid
gas laser, a nitrogen laser, an Ar laser, an He/Ne laser, an He/Cd laser,
a Kr laser or the like; a liquid (dye) laser; a solid laser such as a ruby
laser, an Nd/YAG laser or the like; a semiconductor laser such as a
GaAs/GaAlAs laser, InGaAs laser or the like; an eximer laser such as a KrF
laser, a XeCl laser, a XeF laser, an Ar.sub.2 laser or the like.
In the present invention, an efficiency of removing a silver thin layer
(i.e., it can be said to be a sensitivity of a lithographic printing plate
of the process of the present invention) depends on the thickness of the
silver thin film. A thinner silver thin layer can be easily removed by
runlength is lowered. Thus, it is preferred to determine the thickness of
the silver thin layer according to the laser output power to be used for
imaging. In a plate setter of a heat-mode system presently practiced, an
output on the lithographic printing plate surface is 0.1 to 10 W, and when
these plate setters are employed, a silver amount In the silver thin layer
is preferably 0.1 g/m.sup.2 to 1.5 g/m.sup.2. As a general tendency, when
a laser more than 1 W or more, or when a printing plate for a long run is
to be obtained, the silver amount may be set with a relatively larger
amount. Also, when sensitivity is more important than runlength, that is,
when a laser not more than 1 W is used, the silver amount is preferable
set with a relatively less amount.
EXAMPLES
In the following, the present invention is explained in detail by referring
to Examples, but the present invention is not limited by the following
Examples so long as not exceeding the scope of the present invention.
Incidentally, for calculating a weight ratio of the inorganic oxide, a
solid component described in a brochure is used.
Example 1
On one surface of a PET (polyethylene terephthalate) film having a
thickness of 175 .mu.m and having a 0.04 g/m.sup.2 gelatin subbing layer,
a solution of colloidal silica (available from Nissan Chemical Industries,
Ltd., average particle size: 0.004 to 0.006 .mu.m, 30% sol) and polyvinyl
alcohol with a weight ratio of the colloidal silica being 80% was so
coated to form a hydrophilic layer with a solid content of 2 g/m.sup.2 and
dried.
Next, on the hydrophilic layer, a nuclei coating solution described in
Example 2 of Japanese Provisional Patent Publication No. 21602/1978 (as
physical development nuclei, palladium sulfide is contained, and as a
hydrophilic polymer, No. 3 copolymer described in the above-mentioned
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) is coated and dried.
By maintaining an aqueous solution of inactive gelatin at 60.degree. C.
while vigorously stirring, a mixed aqueous solution of sodium chloride and
potassium bromide (potassium bromide: 29.5 mole %) and an aqueous silver
nitrate solution were simultaneously added thereto to prepare a silver
chlorobromide emulsion having an average particle size of 0.28 .mu.m.
Then, potassium iodide in an amount corresponding to 0.5 mole %/mole Ag
was added to subject to surface substitution. An emulsion containing these
silver halide emulsion particles was coated on the above-mentioned support
in a silver nitrate amount of 3 g/m.sup.2 and dried to obtain a
lithographic printing material. The silver halide emulsion was a
monodispersed silver chloroiodobromide emulsion comprising 70% of silver
chloride, 29.5% of silver bromide, and 0.5% of silver iodide, and 90% by
weight of the whole particles are within the average particle size
.+-.30%.
The thus obtained lithographic printing material was developed for 15
seconds without exposure with a developing solution obtained by adding 40
ml/l of N-methylethanolamine to the diffusion transfer developing solution
described in Example 1 of Japanese Provisional Patent Publication No.
282295/1992, and the gelatin layer was washed off with a flowing water
immediately after development to obtain Lithographic printing plate
precursor 1 in which the silver thin layer was exposed.
When an amount of silver of the thus prepared Lithographic printing plate
precursor 1 was measured by a fluorescent X-ray device (manufactured by
K.K. Rigaku, 3270, trade name), it was 0.80 g/m.sup.2.
Next, the silver thin layer was photographed by a scanning type electron
microscope. Thus, it can be found that it comprises granular silver
particles, and when the size thereof is measured, it can be found that it
is within the range of 0.005 to 0.2 .mu.m.
The hydrophilic layer of this Lithographic printing plate precursor 1 was
exposed to a semiconductor laser with a wavelength of 830 nm and an output
of 0.5 W to obtain a lithographic printing plate (Lithographic printing
plate 1). This Lithographic printing plate 1 was mounted on an offset
printer (3200MCD, trade name, manufactured by Ryobi Imagics Co.), an
etching solution (SLM-OH, trade name, manufactured by Mitsubishi Paper
Mills Ltd.) was spread all over the surface of the plate, and printing was
carried out by using New Champion Black N (trade name, available from
Dainippon Ink Co.) as an ink. As a result, printed materials excellent in
printing image quality without stain at a non-image area could be obtained
from initiation of printing. Moreover, no stain was occurred finally at
printing of 10,000 sheets and printed materials excellent in printing
image quality could be obtained.
Example 2
In the same manner as in Example 1 except for using zirconia (available
from Nissan Chemical Industries, Ltd., average particle size: 0.03 .mu.m,
15% sol) in place of colloidal silica, a lithographic printing plate
precursor 2 was prepared. Then, in the same manner as in Example 1,
Lithographic printing plate 2 was prepared.
By using Lithographic printing plate 2, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 3
In the same manner as in Example 1 except for using titania (available from
Nissan Chemical Industries, Ltd., average particle size: 0.03 .mu.m, 13%
sol) in place of colloidal silica, a lithographic printing plate precursor
3 was prepared. Then, in the same manner as in Example 1, Lithographic
printing plate 3 was prepared.
By using Lithographic printing plate 3, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 4
In the same manner as in Example 1 except for using .delta. alumina
(available from Nippon Aerosil K.K., average particle size: 0.012 .mu.m,
20% sol) in place of colloidal silica, a lithographic printing plate
precursor 4 was prepared. Then, in the same manner as in Example 1,
Lithographic printing plate 4 was prepared.
By using Lithographic printing plate 4, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Comparative Example 1
In the same manner as in Example 1 except for not using colloidal silica
and preparing a hydrophilic layer with polyvinyl alcohol alone,
Lithographic printing plate a was prepared.
By using Lithographic printing plate a, when printing was carried out in
the same manner as in Example 1, a stripe shaped stain occurred at the
non-image area and printing was continued by 1,000 sheets, but the stain
did not disappeared. The printer was stopped, and ink on the plate surface
was wiped with an etching solution and restarted printing. Then, the
degree of the stain was slightly reduced than before, but excellent
printed materials could not be obtained.
Comparative Example 2
In the same manner as in Comparative example 1 except for using gelatin in
place of polyvinyl alcohol, Lithographic printing plate b was prepared.
By using Lithographic printing plate b, when printing was carried out in
the same manner as in Example 1, a stripe shaped stain occurred at the
non-image area as in Comparative example 1 and printing was continued by
1,000 sheets, but the stain did not disappeared. The printer was stopped,
and ink on the plate surface was wiped with an etching solution and
restarted printing. Then, the degree of the stain was slightly reduced
than before, but excellent printed materials could not be obtained.
Example 5
In the same manner as in Example 1 except for using silica (available from
Fuji Silisia Chemical K.K., average particle size: 2.2 to 2.9 .mu.m) in
place of colloidal silica, Lithographic printing plate 5 was prepared.
By using Lithographic printing plate 5, when evaluation of printing was
carried out in the same manner as in Example 1, dot shaped stain occurred
at the non-image area at initiation of printing. The printer was once
stopped and the plate surface was wiped, and printing was restarted. Then,
no dot shaped stain occurred and good printed materials can be obtained.
Example 6
In the same manner as in Example 1 except for using titanium oxide
(available from Ishihara Sangyo K.K., average particle size: 0.2 to 0.4
.mu.m) in place of colloidal silica, Lithographic printing plate 6 was
prepared.
By using Lithographic printing plate 6, when evaluation of printing was
carried out in the same manner as in Example 1, dot shaped stain occurred
at the non-image area at initiation of printing. However, this stain was
naturally disappeared during printing and good printed materials can be
obtained without recurring the stain.
Example 7
In the same manner as in Example 1 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) to which colloidal silica
(available from Nissan Chemical Industries, Ltd., average particle size:
0.004 to 0.006 .mu.m, 30% sol) was added so as to become an amount of 0.1
g/m.sup.2, Lithographic printing plate 7 was prepared.
By using Lithographic printing plate 7, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 8
In the same manner as in Example 1 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) to which zirconia (available
from Nissan Chemical Industries, Ltd., average particle size: 0.03 .mu.m,
15% sol) was added so as to become an amount of 0.1 g/m.sup.2,
Lithographic printing plate 8 was prepared.
By using Lithographic printing plate 8, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 9
In the same manner as in Example 1 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
in an amount of 4 mg/m.sup.2) to which titania (available from Nissan
Chemical Industries, Ltd., average particle size: 0.03 .mu.m, 13% sol) was
added so as to become an amount of 0.1 g/m.sup.2, Lithographic printing
plate 9 was prepared.
By using Lithographic printing plate 9, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 10
In the same manner as in Example 1 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) to which .delta. alumina
(available from Nippon Aerosil K.K., average particle size: 0.012 .mu.m,
20% sol) was added so as to become an amount of 0.1 g/m.sup.2,
Lithographic printing plate 10 was prepared.
By using Lithographic printing plate 10, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 11
In the same manner as in Example 2 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) to which colloidal silica
(available from Nissan Chemical Industries, Ltd., average particle size:
0.004 to 0.006 .mu.m 30% sol) was added so as to become an amount of 0.1
g/m.sup.2, Lithographic printing plate 11 was prepared.
By using Lithographic printing plate 11, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 12
In the same manner as in Example 3 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) to which colloidal silica
(available from Nissan Chemical Industries, Ltd., average particle size:
0.004 to 0.006 .mu.m, 30% sol) was added so as to become an amount of 0.1
g/m.sup.2, Lithographic printing plate 12 was prepared.
By using Lithographic printing plate 12, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 13
In the same manner as in Example 4 except for using a nuclei coating
solution described in Example 2 of Japanese Provisional Patent Publication
No. 21602/1978 (as physical development nuclei, palladium sulfide is
contained, and as a hydrophilic polymer, No. 3 copolymer described in said
publication comprising acrylamide and imidazole which polymer is contained
is used in a coated amount of 4 mg/m.sup.2) to which colloidal silica
(available from Nissan Chemical Industries, Ltd., average particle size:
0.004 to 0.006 .mu.m, 30% sol) was added so as to become an amount of 0.1
g/m.sup.2, Lithographic printing plate 13 was prepared.
By using Lithographic printing plate 13, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 14
In the same manner as in Example 1 except that a hydrophilic layer in which
the ratio of colloidal silica and polyvinyl alcohol in Example 1 was
changed to 90% by weight of colloidal silica was provided, Lithographic
printing plate 14 was prepared.
By using Lithographic printing plate 14, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 15
In the same manner as in Example 1 except that a hydrophilic layer in which
the ratio of colloidal silica and polyvinyl alcohol in Example 1 was
changed to 55% by weight of colloidal silica was provided, Lithographic
printing plate 15 was prepared.
By using Lithographic printing plate 15, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 16
In the same manner as in Example 2 except that a hydrophilic layer in which
the ratio of zirconia and polyvinyl alcohol in Example 2 was changed to
90% by weight of zirconia was provided, Lithographic printing plate 16 was
prepared.
By using Lithographic printing plate 16, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 17
In the same manner as in Example 2 except that a hydrophilic layer in which
the ratio of zirconia and polyvinyl alcohol in Example 2 was changed to
55% by weight of zirconia was provided, Lithographic printing plate 17 was
prepared.
By using Lithographic printing plate 17, when evaluation of printing was
carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 18
By using the Lithographic printing plates 14 to 17, ink/water responses of
these plates were measured. Ink/water response was measured by using a
printer and ink used in Example 1, stopping feed of water during printing,
winding ink to the plate to compulsory stain the plate, feeding damping
water to the plate and a number of papers at which stain at the non-image
area is disappeared was counted. The results are shown in Table 1.
TABLE 1
______________________________________
Lithographic
printing plate 14 15 16 17
______________________________________
Ink/water .smallcircle.
.increment. .smallcircle.
.increment.
response
______________________________________
.smallcircle.: Stain disappeared within 20 sheets of papers.
.increment.: Stain disappeared within 20 to 50 sheets of papers.
x: More than 50 sheets of papers are required until stain disappears.
Examples 19 to 22
In the same manner as in Example 1 except that hydrophilic layers were each
provided so that the weight ratios of colloidal silica in Example 1 based
on the total amount of colloidal silica and polyvinyl alcohol are 20% and
40% by weight, to prepare Lithographic printing plates 18 and 19,
respectively. Moreover, in the same manner as in Example 2 except that
hydrophilic layers were each provided so that the weight ratios of
zirconia in Example 2 based on the total amount of zirconia and polyvinyl
alcohol are 40% and 20% by weight, to prepare Lithographic printing plates
20 and 21, respectively.
By using these Lithographic printing plates 18 to 21, when printing
qualities thereof were evaluated in the same manner as in Example 1, it
was found that all Lithographic printing plates showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Next, by using these Lithographic printing plates 18 to 21, ink/water
responses thereof were measured in the same manner as in Example 18. As a
result, ink/water responses at the time of initiating printing, each
required 50 sheets or more until stain disappears and a weight ratio of
the inorganic oxide was slightly bad as compared with 80% of Examples land
2. However, once the stain disappeared, no stain occurred again. Thus, in
the printing evaluation, all the Lithographic printing plates 18 to 21
showed printability excellent in stain resistance as in Examples 1 and 2.
Example 23
Before effecting printing by using Lithographic printing plate 2, UV
exposure was carried out by using UV lamp F300 (trade name, available from
Fusion Japan K.K.) to prepare Lithographic printing plate 22.
By using this Lithographic printing plate 22, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 24
In the same manner as in Example 23 except for using Lithographic printing
plate 3, Lithographic printing plate 23 was prepared.
By using this Lithographic printing plate 23, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 25
During laser beam exposure of Lithographic printing plate 2, UV exposure
was simultaneously carried out by using UV lamp F300 (trade name,
available from Fusion Japan K.K.) to prepare Lithographic printing plate
24.
By using this Lithographic printing plate 24, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 26
In the same manner as in example 25 except for using Lithographic printing
plate 3 in place of using Lithographic printing plate 2, Lithographic
printing plate 25 was prepared.
By using this Lithographic printing plate 25, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 27
By using Lithographic printing plates 2 and 3 and Lithographic printing
plates 22 to 25, stain tests were carried out under severer conditions
than Example 1. The stain printing test was carried out by using, as an
etching solution, SLM-OD30 (trade name, available from Mitsubishi Paper
Mills Limited) which had been diluted twice than the usual prescription,
and using the printer and ink used in Example 1. The result are shown in
Table 2.
TABLE 2
______________________________________
Lithographic
printing plate 2 3 22 23 24 25
______________________________________
Stain test .increment.
.increment.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
______________________________________
.smallcircle.: No stain occurred.
.increment.: Stain appears at initiating printing but not occurred
thereafter.
x: Stain occurs throughout the printing.
Example 28
On the silver thin layer of Lithographic printing plate 1 prepared in
Example 1, the following overcoating solution (a coating solution for
forming a hydrophilic polymer layer) was so coated that a wet component
coated amount of 15 g/m.sup.2 followed by drying. At this time, the
thickness of the hydrophilic layer was about 0.2 .mu.m.
Overcoating Solution 1
______________________________________
Gum Arabic 10 g
85% phosphoric acid 1 g
Water 900 ml
______________________________________
Adjusted to pH=7.0.+-.0.1 by adding 1 N aqueous sodium hydroxide solution.
The above mixture was made up to 1,000 ml by further adding water.
By using Lithographic printing plate precursor 26 in which the hydrophilic
polymer layer had been provided on the silver thin layer, laser beam
exposure was carried out in the same manner as in Example 1 to prepare
Lithographic printing plate 26.
By using this Lithographic printing plate 26, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 29
In the same manner as in Example 2 except that the above-mentioned
overcoating solution (a coating solution for forming a hydrophilic polymer
layer) was coated on the silver thin layer of Lithographic printing plate
2 prepared in Example 2 so that a wet component coated amount of 15
g/m.sup.2 followed by drying to provide a hydrophilic polymer layer having
a thickness of about 0.2 .mu.m. Thus, Lithographic printing plate
precursor 27 was prepared as in Example 2 and it was subjected to laser
exposure to obtain Lithographic printing plate 27.
By using this Lithographic printing plate 27, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 30
In the same manner as in Example 3 except that the above-mentioned
overcoating solution (a coating solution for forming a hydrophilic polymer
layer) was coated on the silver thin layer of Lithographic printing plate
3 prepared in Example 3 so that a wet component coated amount of 15
g/m.sup.2 followed by drying to provide a hydrophilic polymer layer having
a thickness of about 0.2 .mu.m. Thus, Lithographic printing plate
precursor 28 was prepared as in Example 3 and it was subjected to laser
exposure to obtain Lithographic printing plate 28.
By using this Lithographic printing plate 28, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 31
In the same manner as in Example 4 except that the above-mentioned
overcoating solution (a coating solution for forming a hydrophilic polymer
layer) was coated on the silver thin layer of Lithographic printing plate
4 prepared in Example 4 so that a wet component coated amount of 15
g/m.sup.2 followed by drying to provide a hydrophilic polymer layer having
a thickness of about 0.2 .mu.m. Thus, Lithographic printing plate
precursor 29 was prepared as in Example 4 and it was subjected to laser
exposure to obtain Lithographic printing plate 29.
By using this Lithographic printing plate 29, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Examples 32 to 35
In the same manner as in Examples 28 to 31 except for providing the
hydrophilic polymer layer having a thickness of about 0.6 .mu.m by coating
the overcoating solution 1 repeatedly to prepare Lithographic printing
plates 30, 31, 32 and 33, respectively. To these Lithographic printing
plates 30 to 33, exposure was carried out with a semiconductor laser with
a wavelength of 830 nm and a power of 0.5 W, but removal of the silver
thin layers at the non-image area were insufficient and the silver thin
layers remained with a stripe shape. Also, when printing was carried out
in the same manner as in Example 1 by using the above Lithographic
printing plates 30 to 33, stripe-shaped stains occurred at the non-image
portion at initiating the printing. However, when the printer was stopped,
the plate surface was wiped and printing was restarted, then the
stripe-shaped stain was disappeared in the respective Lithographic
printing plates.
Example 36
In the same manner as in Example 28 except for changing the overcoating
solution 1 prepared in Example 28 with the following overcoating solution
2, Lithographic printing plate precursor 34 was prepared from Lithographic
printing plate precursor 1 prepared in Example 1, and Lithographic
printing plate 34 was prepared by exposure.
By using this Lithographic printing plate 34, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Overcoating Solution 2
______________________________________
Monoethanolamine 5 g
3-n-Octyl-5-mercaptoxazole 0.2 g
Gum Arabic 10 g
Sodium dihydrogen phosphate 10 g
85% phosphoric acid 1 g
Water 900 ml
______________________________________
Adjusted to pH=7.0.+-.0.1 by adding 1 N aqueous sodium hydroxide solution.
The above mixture was made up to 1,000 ml by further adding water.
Example 37
In the same manner as in Example 29 except for changing the overcoating
solution 1 prepared in Example 29 with the above overcoating solution 2,
Lithographic printing plate precursor 35 was prepared from Lithographic
printing plate precursor 2 prepared in Example 2, and Lithographic
printing plate 35 was prepared by exposure.
By using this Lithographic printing plate 35, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 38
In the same manner as in Example 30 except for changing the overcoating
solution 1 prepared in Example 30 with the above overcoating solution 2,
Lithographic printing plate precursor 36 was prepared from Lithographic
printing plate precursor 3 prepared in Example 3, and Lithographic
printing plate 36 was prepared by exposure.
By using this Lithographic printing plate 36, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 39
In the same manner as in Example 31 except for changing the overcoating
solution 1 prepared in Example 31 with the above overcoating solution 2,
Lithographic printing plate precursor 37 was prepared from Lithographic
printing plate precursor 4 prepared in Example 4, and Lithographic
printing plate 37 was prepared by exposure.
By using this Lithographic printing plate 37, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 40
By using Lithographic printing plates 26 to 29 and 34 to 37 prepared as
mentioned above, stain tests were carried out under the conditions of
easily causing stain as in Example 27. The results are shown in Table 3.
TABLE 3
______________________________________
Lithographic
printing plate 26 27 28 29 34 35 36 37
______________________________________
Stain test
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
______________________________________
.smallcircle.: No stain occurred.
.increment.: Stain appears at initiating printing but not occurred
thereafter.
x: Stain occurs throughout the printing.
Example 41
By using Lithographic printing plate precursors 1 to 4, Lithographic
printing plate precursors 26 to 29 and Lithographic printing plate
precursors 34 to 37, laser beam exposure was carried out after one week
from the day when the silver thin layers were prepared to prepare
Lithographic printing plates 1A to 4A, 26A to 29A and 34A to 37A,
respectively. Moreover, laser beam exposure was carried out after one
month from the day when the silver thin layers were prepared to prepare
Lithographic printing plates 1B to 4B, 26B to 29B and 34B to 37B,
respectively. Next, printing characteristics thereof were examined.
As a result, in samples prepared after one week, all the Lithographic
printing plates 1A to 4A, 26A to 29A and 34A to 37A are good in stain, but
in Lithographic printing plates 1A to 4A, an ink density at the image area
was lowered. Also, in samples prepared after one month, no specific
problem occurred in stain, but in Lithographic printing plates 1B to 4B,
an ink density at the image area was further lowered, and also in
Lithographic printing plates 26B to 29B, lowering in ink density at the
image area was slightly observed. However, in Lithographic printing plates
34B to 37B, no lowering in density at the image area was observed and
excellent printed matter can be obtained.
Example 42
In the same manner as in Example 36 except for using a paper base
(thickness: 175 .mu.m) coated by polyethylene having a gelatin subbing
layer with 0.04 g/m.sup.2 as a support, Lithographic printing plate 38 was
prepared.
By using this Lithographic printing plate 38, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Example 43
In the same manner as in Example 37 except for using a paper base
(thickness: 175 .mu.m) coated bypolyethylene having a gelatin subbing
layer with 0.04 g/m.sup.2 as a support, Lithographic printing plate 39 was
prepared.
By using this Lithographic printing plate 39, when evaluation of printing
was carried out in the same manner as in Example 1, it showed printability
excellent in stain resistance as in Lithographic printing plate 1.
Examples 44 to 46
Lithographic printing plate precursors were prepared in the same manner as
in Example 1 except for changing a coated amount of the emulsion layer to
a silver nitrate amount of 5 g/m.sup.2 and developing time to 5 seconds,
20 seconds and 15 seconds, respectively, and the above-mentioned
overcoating solution 2 was coated with a thickness of about 0.2 .mu.m
(Lithographic printing plate precursors 40, 41 and 42, respectively).
Next, silver amounts of these Lithographic printing plate precursors 40,
41 and 42 were measured in the same manner as in Example 1. The results of
silver amounts measured were shown in Table 4.
TABLE 4
______________________________________
Lithographic
printing plate 40 41 42
______________________________________
Silver amount
0.23 1.41 0.67
(g/m.sup.2)
______________________________________
By using these Lithographic printing plate precursors 40, 41 and 42,
respective hydrophilic layers were exposed by a semiconductor laser with a
wavelength of 830 nm and a power of 0.5 W in the same manner as in Example
1 to obtain Lithographic printing plates 40 to 42, respectively.
Next, in the same manner as in Example 1, printing was carried out by using
the above Lithographic printing plates 40 to 42. In Lithographic printing
plate 42, as in Example 1, printed matter excellent in printing quality
without any stain at the non-image area can be obtained from initiation of
printing. Also, no stain occurred finally with 10,000 sheets of printing
and printed matter excellent in printing quality can be obtained. In
Lithographic printing plate 40, printed matter excellent in printing
quality without any stain at the non-image area can be obtained from
initiation of printing. However, in printing up to 10,000 sheets, missing
of a fine line at the image area was observed. In Lithographic printing
plate 41, stain occurred at the non-image area at initiation of printing
but the stain shortly disappeared. Thereafter, the stain did not recur up
to 10,000 sheets of printing and printed matter excellent in printing
quality can be obtained.
Examples 47 to 49
Lithographic printing plate precursors were prepared in the same manner as
in Example 2 except for changing coated amount of the emulsion layer to a
silver nitrate amount of 5 g/m.sup.2 and developing time to 5 seconds, 20
seconds and 15 seconds, respectively, and the above-mentioned overcoating
solution 2 was coated with a thickness of about 0.2 .mu.m (Lithographic
printing plate precursors 43, 44 and 45, respectively). Next, silver
amounts of these Lithographic printing plate precursors 43, 44 and 45 were
measured in the same manner as in Example 1. The results of silver amounts
measured were shown in Table 5.
TABLE 5
______________________________________
Lithographic
printing plate 43 44 45
______________________________________
Silver amount
0.15 1.38 0.49
(g/m.sup.2)
______________________________________
By using these Lithographic printing plate precursors 43, 44 and 45,
respective hydrophilic layers were exposed by a semiconductor laser with a
wavelength of 830 nm and a power of 0.5 W in the same manner as in Example
1 to obtain Lithographic printing plates 43 to 45, respectively.
Next, in the same manner as in Example 1, printing was carried out by using
the above Lithographic printing plates 43 to 45. In Lithographic printing
plate 45, as in Example 1, printed matter excellent in printing quality
without any stain at the non-image area can be obtained from initiation of
printing. Also, no stain occurred finally with 10,000 sheets of printing
and printed matter excellent inprinting quality can be obtained. In
Lithographic printing plate 43, printed matter excellent in printing
quality without any stain at the non-image area can be obtained from
initiation of printing. However, in printing up to 10,000 sheets, missing
of a fine line at the image area was observed. In Lithographic printing
plate 44, stain occurred at the non-image area at initiation of printing
but the stain shortly disappeared. Thereafter, the stain did not recur up
to 10,000 sheets of printing and printed matter excellent in printing
quality can be obtained.
Examples 50 to 52
By using Lithographic printing plate precursors 40 to 42 prepared in
Examples 44 to 46, image was formed by using a YAG laser with a wavelength
of 1064 nm and a power of 8 W in place of the semiconductor laser used in
Examples 44 to 46 to prepare Lithographic printing plates 40A to 42A,
respectively. Printing was carried out in the same manner as in Example 1
by using Lithographic printing plates 40A to 42A. The results are shown in
Table 6.
TABLE 6
______________________________________
Lithographic
printing plate 40A 41A 42A
______________________________________
Printing stain
.smallcircle.
.increment.
.smallcircle.
Missing of image .increment. .smallcircle. .smallcircle.
______________________________________
Printing stain
.smallcircle.: No stain at nonimage area and thus good.
.increment.: Stain occurred at initiation of printing but thereafter good
x: Stain occured throughout the printing.
Missing of image
.smallcircle.: No missing of image at image area and thus good.
.increment.: No missing of image up to 2,000 sheets of printing and thus
good.
x: Missing of image occurred within 2,000 sheets of printing.
Examples 53 to 57
By using Lithographic printing plate precursors 43 to 45 prepared in
Examples 47 to 49, image was formed by using a YAG laser with a wavelength
of 1064 nm and a power of 8 W in place of the semiconductor laser used in
Examples 47 to 49 to prepare Lithographic printing plates 43A to 45A,
respectively. Printing was carried out in the same manner as in Example 1
by using Lithographic printing plates 43A to 45A. The results are shown in
Table 7.
TABLE 7
______________________________________
Lithographic
printing plate 43A 44A 45A
______________________________________
Printing stain
.smallcircle.
.increment.
.smallcircle.
Missing of image .increment. .smallcircle. .smallcircle.
______________________________________
Printing stain
.smallcircle.: No stain at nonimage area and thus good.
.increment.: Stain occurred at initiation of printing but thereafter good
x: Stain occured throughout the printing.
Missing of image
.smallcircle.: No missing of image at image area and thus good.
.increment.: No missing of image up to 2,000 sheets of printing and thus
good.
x: Missing of image occurred within 2,000 sheets of printing.
As explained above, in the process for making a lithographic printing plate
of the present invention, the operation can be carried out under a room
light and operation surroundings are extremely good since no developing
solution is used. Also, the process can respond to the direct imaging
method by a laser beam whereby an excellent effect can be obtained that an
image with high resolution can be obtained with a lowcost. Moreover, a
lithographic printing plate excellent in ink/water response can be
provided.
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